Manufacturing facilities, such as automobile assembly plants, use moving skillets to convey large parts throughout the facility. The skillets are commonly larger than the workpiece to provide a platform for a worker to perform production tasks while the skillet is in motion. In other words, the skillet may form a moving floor, allowing the worker to perform a production task while moving with the skillet and workpiece. When the production task is complete, the worker may leave the skillet by walking to an adjoining skillet or stepping from the skillet to the floor of the facility or to a platform adjacent to the skillets. The skillet typically moves along a predetermined path in a pit and the upper surface of the skillet is generally somewhat aligned with the floor of the facility or a platform extending along at least portions of the skillet path.
While assembly plants have multiple designs, one common design is to have the skillet assembly (skillet and coupled workpiece) move through multiple production and delivery areas. More specifically, the skillet assembly is commonly moved from production area to production area until all of the assembly steps are completed. The workpiece is then separated and the skillet is returned to the start of the assembly line. Each production area is typically dedicated to a particular production task, or series of tasks, wherein the length of each production area, speed with which the skillet moves through the production area, and the type of mechanical equipment and tools needed depends on the nature and number of tasks assigned to that production area.
The skillets are brought together in production areas to form a continuous moving platform, floor, or “train” upon which the production tasks can be performed. The front and back ends of each skillet are typically adapted to adjoin the back and front ends of adjacent skillets. Having the skillets abutted together in production areas enables workers to move around the workpieces, as well as from skillet to skillet, to efficiently accomplish the tasks assigned to that production area.
The multiple production areas may be separated from one another by delivery areas to facilitate part storage, walkways, and other effective use of floor space between each production area. Once the skillet assemblies pass through the production area, the skillets typically enter a delivery area where they are separated and moved to the next production area. Separate accelerating drives can also be provided to move the skillets from the production area to the delivery area and to establish proper spacing between adjacent skillets in the delivery areas. In delivery areas, the skillet assemblies may be spaced a predetermined distance from one another, allowing faster speeds and fewer required skillets and thereby lowering the cost of the system through limiting the total number of skillets. The system may include various indexing stations, accelerators, and decelerators in the delivery area to provide proper skillet spacing and speed. Indexing in the delivery areas allows the skillets to enter each production area in a timely manner so that the next production area continually receives skillets to keep the skillets in the next production area moving at the desired rate. An accumulation of skillets known as “float” before the skillets enter the next production area is also helpful in preventing downstream production areas from stopping, even momentarily, due to a lack of skillets. The float allows for upstream production areas to stop the skillets while tasks are performed or to temporarily stop movement of the skillets in the production area to fix a problem without disrupting a downstream production area.
Each of the above components requires drive, safety, and control units to ensure proper delivery of each skillet assembly to and through the respective production areas. Friction drive assemblies, such as drive wheels that engage the sides of the skillets, are commonly provided at or near the entrance to each production area, to convey each skillet assembly into and through the production area at a predetermined speed. With skillets abutted together, the entire train of skillets may be driven by a single drive mechanism engaging a single skillet, i.e., one skillet can push downstream skillets in the production area. Return or retarder drives, typically located at the end of a production area, are often provided to ensure, if necessary, that the skillets are kept abutted to one another and do not separate as they travel through the production area.
One feature common among skillets in production facilities is the need to have electrical power for completing production tasks. It is typical for each skillet to have electrical power throughout the production area to power various electrical equipment, such as, tools, lifts, current disconnects, controls, diagnostic lights or indicators, tool plug-in outlets, clamps, compressors, pumps, emergency stops, or any other necessary or helpful electrical tool. In conventional conveyor systems, an electrical conductor, such as an electrified rail, is commonly run along the entire length of the conveyor path within the production area. This conductor is commonly underneath the skillets, supplying power to the moving skillets. The skillets each include a power receiving device, such as a connector shoe, extended from the skillet that engages the conductor to receive the electrical power. To continuously supply power to the skillet, the collector shoe must continuously contact the conductor throughout any period that requires the skillet to be electrically powered. To continuously supply electrical power throughout the production area, the conductor is extended the entire length of the production area so that each collector shoe always stays in contact with the conductor along the entire length of the production area. One drawback common to these systems is increased manufacturing costs due to excessive conductor lengths. The extended length of the conductor also increases the total friction of the system, as each collector shoe stays engaged on the conductor throughout the production area, requiring more powerful drive systems, especially in long production areas. Furthermore, the collector shoes staying engaged on the conductor throughout the length of the production area also increases wear of the collector shoes and conductor, increasing replacement, maintenance, and repair costs.
Therefore, there is a need for a system with less manufacturing, installation, replacement, and maintenance costs that still allows the skillets to be abutted together in the production area and have power supplied to each skillet in the production area. More specifically, there is a need for a system that eliminates the necessity of having a conductor that extends the length of each production area and reduces wear associated with the multiple collector shoes being in contact with the conductor along the entire production area.